Total Knee Replacement
All about Total Knee Replacement (TKR)
TKR is a major operation on the knee in which the worn out surfaces of the joint are replaced, or more accurately, resurfaced, with metal and plastic. (It is not a matter of chopping out the whole knee joint and inserting a bionic one!) In the process, any bow legged or knocked knee deformity is usually corrected back to normal. In addition, every effort is made to regain full straightening of the knee, which may have been lost with the stiffening of arthritis, and also to maximise the amount of knee bend. The medial and lateral ligaments on the inner and outer sides of the knee are preserved but one or both of the cruciate ligaments are routinely removed as they are no longer required. The patella (knee cap), may or may not be resurfaced also, depending on your surgeon’s preference and whether your particular knee suffers a lot of pain from the patella as well, and/or suffers predominantly inflammatory arthritis. If there is no significant patella pain with activity, and especially if you are younger than average for a knee replacement, I prefer not to resurface the patella, but most of the time it is better to do so.
Knee replacement surgery is a major procedure, and not to be entered into lightly. Other treatment options need to have been explored first. Sometimes, especially on X-Ray reports, it may be said that you have arthritis, but it may just be some fairly minor wear and tear.
What is Arthritis?
Arthritis literally means “inflammation of a joint”. In this context however, we are talking about the end stage of joint damage by one or more of the following causes:
Wear and tear (osteoarthritis)
Inflammatory disease (eg rheumatoid arthritis)
Severe injury (post traumatic arthritis) or
Infection (septic arthritis).
Osteoarthritis is the most common reason for needing a TKR. It usually comes on as a gradual wear and tear process over thirty years or so but on occasion it may be a much more rapid breakdown process associated with painful inflammation and swelling. Predisposing factors to the gradual development of osteoarthritis are: having a family tendency, or a genetic predisposition, tearing and/or removal of a cartilage (meniscus), and repetitive minor injuries as may occur in a long career in contact sports.
Quite often, when you have had X-rays, the report may say that you have osteoarthritis, when really the wear and tear changes are still quite minor. To my mind, osteoarthritis is when the joint surfaces have worn right down to bone on bone. Until then, it is just varying degrees of wear and tear (degeneration).
How do I know if and when I need a knee replacement?
A knee replacement is the final solution for when arthritis has become so bad, and significantly limiting to one’s already quiet lifestyle, that all other treatment options have been used up and no longer adequately manage the problem. Usually, the key problem is that you simply can’t walk very far at all. How far that might be when it becomes unacceptable is variable for different people. Some persevere till they can barely manage 100 metres, while for others, it may be 500 metres or more. Or maybe you can't play golf any more. Other factors that may push to make the decision to go for surgery include pain that wakes you up through the night, pain that prevents you being able to get up or down steps, increasing deformity and malalignment of the leg, or a limp that causes aggravation of pain elsewhere such as the lower back or somewhere in the other lower limb. In the end, it becomes a matter of balancing the magnitude of the operation and the recovery, and the possible risks involved, with the likely benefits to be expected from having had the operation. Your surgeon is a good person to discuss the decision making process with, and to get perspective on just what to expect. The further information here will hopefully prepare you well for that discussion.
Length of Recovery Time
Before we rush into this decision, it is important to know what you are letting yourself in for! A Knee Replacement is major surgery, and there are risks, and complications can and do occur. It will knock you around a bit, and you will feel quite tired for several weeks probably. After the operation it should be possible to go home after about 6 days, although for the first two weeks at home, you would still be quite limited and need plenty of home help. At six weeks after the operation you should be getting around reasonably well day to day but it takes at least three months, and usually 6 months or so to really get over the operation. Some swelling, stiffness, soreness or clicking may persist for some time, and many people feel that some further minor improvement continues for over a year.
How can I keep my knee going and put off the need for a knee replacement?
Total knee replacement (TKR), is the final solution for a knee that has been destroyed by arthritis, resulting in painful grinding of bone on bone. By the time the pain is bad enough to need a total knee replacement, it will seriously interfere with lifestyle, significantly limiting how far you can walk without having to sit down or use a walking stick (or lean on a shopping trolley at the supermarket).
The pain may also wake you at night. It will have reached the stage that it can no longer be managed adequately with pain killers (eg Panadol Osteo) and/or anti-inflammatories (arthritis medication, also known as NSAID's). Sometimes it can take a bit of trial and error to find an anti-inflammatory that works for you, without causing undue side effects such as indigestion, or upsetting your blood pressure. Many people also find that large doses of fish oil (10 mls a day, 10 standard strength capsules a day, or 3-4 of a triple strength formula fish oil), and dietary supplements for joints like glucosamine and chondroitin sulphate, or turmeric, might help manage the arthritic symptoms for some time. In fact, studies show that glucosamine may actually slow down the arthritic process in some people.
Further options that may or may not work, include injections either of platelet rich plasma, or hyaluran. Platelet rich plasma (PRP) is taken from your own blood which is spun down to separate the cells and the serum, and the PRP is the small percentage in between. The platelets carry a lot of growth factors, some of which are really helpful. So far, we can’t choose which growth factors to inject, so it is bit hit and miss how much benefit you might get. By comparison, stem cell treatment is very much more expensive, unsterile, and offers no advantage over PRP.
Hyaluran is a macro-molecule which is part of the articular cartilage and in the normal joint fluid. There are a few different brands including Synvisc, Durolane and Euflexxa. We don’t know exactly how it works, although the advertising promotes it as a joint lubricant. It doesn’t stay long in the joint fluid however. I think it works by kind of resetting the biochemistry in your knee, but again, it is hit and miss. About 20% of people get really good results, and then the injection can be repeated every 6-8 months indefinitely. Another 40% or so get some benefit, while the last 40% don’t get any benefit at all, so it is a matter pay your money and take the chance. Other contributing factors in the decision to have a knee replacement may include that there is increasingly severe deformity or restriction of range of movement. Also, the tendency to limp may aggravate other problems, such as chronic low back pain, or pain in the other knee, to the extent that it all gets too hard to continue to cope.
In assessing the severity of your arthritis, X-rays taken while standing can confirm that the gristle lining (articular cartilage) of the joint surfaces is completely worn out down to bare bone, but this is not the main deciding factor. Some people’s knees look awful, but are not all that painful, while others may develop quite rapidly progressive arthritis with a lot more pain than might otherwise be expected for X-rays that don’t look all that bad at the time.
If you think maybe your knee is not ready for a knee replacement after all, you may wish to read more about wear and tear. (I only call it arthritis when it is down to bone on bone.)
How old is too old or too young?
If you are healthy enough to be able to walk, you are never too old for a knee replacement. If your health is very poor, there is probably a greater risk from the anaesthetic and the magnitude of the operation and that would need to be individually assessed, to decide if the potential benefits would out-weigh the risks.
If you are rather young to be suffering arthritis (under 60, or especially if you are under 50), your doctors would tend to try to put off the operation for as long as you can manage, because a joint replacement does not last forever. It may last twenty years but sooner or later it will wear out and/or become loose and need to be revised (changed over to a new one) in another more major operation. If you are young and/or active and/or very overweight, a joint replacement may fail even within ten years.
Ideally we would prefer that your knee replacement would last the rest of your life but if your arthritis is bad enough and can not be managed any other way, there is no fixed lower age limit for the operation. However, we do know that the younger you are when the operation is done, the higher the short to medium term failure rate, statistically.
Getting Ready for the Operation
Having made the decision to go ahead, your doctor will organise some blood tests and perhaps a further X-ray and/or CT scan to help in the technical planning of the operation. These days the Blood Bank tends to recommend donor blood rather than your giving your own blood, as it is fresher, and the risks are minimal. A blood transfusion has become quite uncommon ow that we routinely use the drug tranexamic acid at the time of the surgery to minimise bleeding.
You may benefit from seeing a Physiotherapist beforehand to acquaint yourself with the exercises that will be required afterwards and to optimise strength and movement in preparation for the surgery.
It is a good idea to attend an education and orientation session at the hospital in the week or so before surgery for the nurses to acquaint you with the surroundings and what can be expected to happen on the big day and afterwards.
Many surgeons make it a routine requirement that you see a specialist physician prior to the surgery, to make sure that your general health is as good as it can be, in preparation for the surgery. Medical complications can and do occur after what is quite major surgery, and especially considering that most people having this surgery are getting on in years. This physician would then be the person who would see and treat you if any medical post-operative complications should occur, so it would be good for them to be acquainted with you beforehand. In addition, especially if you are in poor health, or there is any potential problem with having an anaesthetic, you will probably be asked to attend a pre-anaesthetic consultation so that your anaesthetist can get to know you and your health problems, and be prepared to provide the best possible care on the day.
If the physician and/or the anaesthetist has any concerns about the risk of the surgery in your case, they would recommend that it be done in a hospital with an Intensive Care Unit. For example, while I do most of my surgery at the Sportsmed-SA hospital, which is truly excellent in all respects, if an ICU may be required, I would usually do the surgery at Calvary Hospital North Adelaide, which I can also recommend highly.
Obesity
A major contributing factor to most risks is if you are morbidly obese, with a BMI over 40. I would very strongly recommend that anyone heavier than that be required to get their weight down below that level before surgery, as the complication rate really starts to skyrocket over a BMI of 40. The weight loss not only makes the surgery safer, but also makes you feel much better in yourself, and I encourage people to keep going with the program, and get their BMI down below 35. The problem with weight loss when you have disabling arthritis, and indeed just with older age, is that you really can’t exercise the weight off. The answer is a low calorie, low carb diet, usually with meal substitutes and lots of green vegies so you don’t have to go hungry. If you are effectively burning fat, it usually means that you must have a ketotic breath, (like nail polish remover on your breath), and if you don’t have that, the diet is probably not working.
In Hospital
The Operation
Is done under a general anaesthetic, or an epidural block, which is something that your anaesthetist will talk to you about beforehand. It is done through a long curved incision (about 15cm) down the front of the knee, which inevitably results in some numbness on the outer side of the scar afterwards. The patella is shifted to one side to allow access, and the worn out joint surfaces are chamfered off using special jigs to guide the saw cuts. A trial of the correct size of each of the femoral and tibial components is fitted to the cuts surfaces, and the ligament balance and overall alignment of the limb is checked. I always use computer navigation to ensure that the alignment is exactly where I want it to be. The ideal is to correct any malalignment that existed beforehand to within 3 degrees of neutral, but not to overcorrect. It is at this stage that any fine tuning of alignment or ligament tightness is done by recutting the tibial joint surface, increasing the thickness of the plastic liner, or releasing any excessive ligament tightness on one side or other of the joint.
A decision will have been made before the operation whether or not to resurface the patella with a plastic button, based on whether you had pain from that area, and taking into account your age. The appearance of the surface of the patella at the time of the surgery has been shown scientifically not to matter in determining whether the patella should be resurfaced.
Once everything has been correctly prepared and aligned, the definitive prosthetic components are then opened and inserted. The final alignment is rechecked with the computer navigation, and the knee is meticulously sewn up. I use two drains from within the joint to ensure that bleeding does not cause excessive swelling afterwards. In addition, the anaesthetist gives you an injection to minimise the extent of bleeding that occurs.
Pain Relief
A lot of surgeons infiltrate lots of local anaesthetic all around the joint during the operation, which also works very well, but I prefer the use of a femoral nerve block, which seems to give better pain relief, often lasting for up to 24 hours. In addition, pain relief is usually provided intravenously initially with you controlling the dose by pressing the button (don’t under do it!), and/or by injections, then graduating to strong tablets (eg: Tramadol, Endone, Panadeine Forte).
The first three days are not easy, but then most people feel that they “turn the corner” on the third day. A physiotherapist helps with movement, muscle exercises, and with walking, initially with a walking frame, and graduating to a walking stick. Regaining movement is also usually assisted by spending some time on a movement machine (CPM – continuous passive motion) each day, until it is possible to get to 90 degrees of bend on your own. Most people find this very helpful and actually reasonably comfortable.
By day 4 or 5, if all is going well, you would expect to be ready to go home, having had the physio make sure you are safe to get up and down steps. You should be able to fully straighten the knee, and lift your leg with it locked fully straight with good muscle control. The knee should bend to 90 degrees. You should be confident walking with the support of just a walking stick. Arrangements will be made for further follow-up with physiotherapy, hydrotherapy, and to see your doctor to keep an eye on progress.
What are the risks of TKR?
Any operation carries some risks such as wound healing problems, and no operation is guaranteed to be successful. In addition, there are some particular risks with a knee replacement, but overall, knee replacement surgery is highly successful with about 95% of people achieving good results, in terms of being able to walk further without the pain that was there before. 90% of people can walk as far as they like. However, TKR does not aim to restore a normal knee, and there is usually some residual stiffness, and perhaps some discomfort. There is always residual numbness to the outer side of the scar. 20% of people have difficulty getting up and down stairs. It is unusual to be able to squat down, and while it does no harm to the knee to kneel, it doesn’t feel right, and so 50% of people choose not to, even if they can. For about 30% of people, it just too sore to be able to.
The main particular risks of concern are infection or blood clots.
Antibiotics are given at the time of knee replacement surgery and afterwards, and meticulously sterile procedures are followed in order to minimise the risk of infection but there is still an irreducible 0.5% chance of infection occurring, despite our best efforts. If infection gets into the joint it may not be able to be eliminated by antibiotics alone. Then the usual solution is to take out the metal and plastic components (the prosthesis), give high dose antibiotics for about six weeks in hospital and then redo the knee replacement. The success rate after that is down to about 85% and the final result would not be as good as it would have been if completely successful the first time around.
Antibiotics and Dental Work
There is also a small risk of infection getting into the joint even years later, if bacteria get into the blood stream from any infection in your system or even from having some dental work done. While this risk is minimal after the first 6-12 months, or however long it takes for the inflammation of the healing response to settle down, it is arguably still worth taking a dose of antibiotics (if you know you're not allergic) rather than take even a 1 in a 1000 risk on such occasions.
The other major risk that we are concerned about is a blood clot (DVT – deep venous thrombosis). Minor clots in the veins of the calf are quite common and do no harm. If the clot extends into larger veins, it can damage the circulation in the leg for the future. If a piece of clot should break off and go into the lung (pulmonary embolus), that may not cause much trouble if it is small, but on the other hand it could be life-threatening, and you could get very unwell and short of breath indeed.
The best and safest way of preventing blood clots is still somewhat controversial as there is some risk of bleeding complications from the most effective preventative treatments. However, at Sportsmed we have been using a protocol that has been proven to exceed or match world’s best practice. We use 20mg injections of Clexane twice a day to even out the risks of bleeding and clotting that may occur with 40mg once a day, plus calf compression devices to keep the circulation flowing while you are resting in bed. In addition, calf exercises, starting walking as soon as possible, knee movement exercises, and elastic stockings are all routine and all help. Once you go home, we routinely advise taking low dose aspirin for 6 weeks, and continuing with the elastic stockings for that time as well, as the risk of DVT doesn’t completely cease till then.
If you are more at risk than most, eg very overweight, on hormone replacement treatment (HRT), or if you have a family member who has had a blood clot, or especially if you have previously had a thrombosis yourself, you would probably be prescribed higher doses of anti-coagulants.
In addition, we now routinely use tranexamic acid in every case as it has been shown to minimise bleeding into the knee, and also to markedly reduce the need for a blood transfusion after the surgery.
In addition to the risk of blood clots, there are also the very small risks of major complications such as heart attack or stroke, if you are prone to such problems. In fact, there is about 1 chance in 1000 of dying from this major operation. This is why it is so important to have a thorough check-up before the surgery.
Obesity
A major contributing factor to most risks is if you are morbidly obese, with a BMI over 40. I would very strongly recommend that anyone heavier than that be required to get their weight down below that level before surgery, as the complication rate really starts to skyrocket over a BMI of 40. The weight loss not only makes the surgery safer, but also makes you feel much better in yourself, and I encourage people to keep going with the program, and get their BMI down below 35. The problem with weight loss when you have disabling arthritis, and indeed just with older age, is that you really can’t exercise the weight off. The answer is a low calorie, low carb diet, usually with meal substitutes and lots of green vegies so you don’t have to go hungry. If you are effectively burning fat, it usually means that you must have a ketotic breath, (like nail polish remover on your breath), and if you don’t have that, the diet is probably not working.
Apart from these particular concerns, the most likely problem to be encountered after a knee replacement is simply that the knee fails to settle as well or as quickly as expected. 5-10% or so of people suffer significant ongoing problems which may include swelling, stiffness, clicking, aching or twinges of sharp pain. These problems often have an identifiable reason, such as micro-loosening of one of the components, with or without slight subsidence if the bone is a bit weak, or low grade infection, or perhaps just an unusually intense healing response resulting in chronic inflammation and excessive scar tissue formation in the joint (arthrofibrosis). These problems are not usually as troublesome as the arthritis pain from beforehand, but still need to be investigated. Depending on the nature of the problem, further treatment may be required, with variable degrees of success. In the event that you encounter such difficulties, you would expect your surgeon to make an extra effort to explain the problems and possible solutions and outcomes, and continue to support you through what would be a very trying and unexpectedly prolonged recovery. In the end, there are about 10% of people who are not happy with their knee replacement, with the final result falling short of the reasonable expectations you would have had prior to the initial surgery.
How Good is the Knee after a Knee Replacement?
If all goes well, your new knee should be good enough that you can walk as far as you like without pain or swelling. The knee will not feel normal however. It may not go fully straight even though you will be encouraged to work hard to achieve that. Bending should at least go past 90° and we aim for 120° of flexion. More than that is a handy bonus.
According to a number of studies from international centres of excellence, there is a 90% probability that you will be happy enough with your knee replacement, provided that your expectations are realistic. If you are a bit more demanding of your knee, there is about 80% chance that you will be happy that you will be able to bend enough to get back to gardening and go down steps foot over foot, and other activities that require more than an average degree of fairly comfortable bending.
Acceptable activities include golf, swimming, light cycling or walking which can keep you fit and healthy. A bit of social tennis on grass may be possible but it is not actually recommended.
The kinds of activities that you should not pursue are any strenuous or especially jarring or twisting movements. Running and more strenuous work or sport, or even just having to be on your feet all day at work, should be avoided if you want your knee replacement to last. If you are determined to get back to such activities afterwards, your surgeon would at least advise you of the risks involved, so that you could make an educated decision to ignore the routine medical advice, and be aware that you would probably need further surgery within 12 years or so because of wear of the plastic liner.
If it is successful initially and you are not particularly active, there is up to 90% chance your knee could last 20 years or more, according to most experienced surgeons. So far, the National Joint Replacement Register has statistics out to 15 years, with the very best models of knee replacement prosthetic components still surviving about 95% of the time. Excessive load or overuse on the other hand can cause the knee to wear out or loosen in less than 10 years. Moderately active people should be able to expect 15 years or so from their knee before it shows serious signs of wear, as in these X-rays.
Follow-up
So, for the foregoing reasons of wear, possible erosion of the bone causing bone cysts, and possible loosening, you would be well advised to see your GP to have X-rays, and a check-up with your surgeon in the event that you start to get a bit of swelling or aching affecting your knee replacement, especially from 10 years onwards, to identify early wear of the plastic liner in your knee. (Or even wear down to the metal as on the right.) The problem is that there will definitely be wear of the plastic over the years in any case, and much faster if you are heavy and/or very active.
The microscopic wear debris is taken up in the joint lining, and eventually this sets up a chronic inflammatory reaction and swelling. The real concern is that the resulting inflammatory joint lining (synovitis) can eat into the bone supporting the prosthetic components, resulting in erosions and cysts, as we see here (right). If ignored, this inevitably would result in loosening, or even catastrophic collapse of the supporting bone, or spontaneous fracture. If that were allowed to occur, you would need very major revision surgery to take out the previous components, bone graft the defects and put in a whole new knee replacement, as on the left, which never recovers to be quite as good as a good original result.
If the plastic wear is picked up at a fairly early stage, however, it is a much simpler procedure to change over the plastic liner, and clean out the synovitis, following which the knee should recover to be as good as before. This is why it is a good idea to have routine long term follow-up with check X-rays every few years or so, particularly if you are quite active, and your knee replacement was 10-15 years ago or more.
